In a particular application, the system for dispensing is intended to be provided on bottles used in perfumery, in cosmetics or for pharmaceutical treatments. Indeed, this type of bottle conventionally comprises a reservoir for conditioning the product which is returned under pressure by a device for sampling with manual actuation by means of a push-button which is arranged in order to allow for the spraying of the product.
To do this, the device for sampling has a body mounted on the reservoir, said body incorporating means for dispensing which are supplied with the conditioned product by the intermediary of a plunger tube arranged in said reservoir. Moreover, the body is provided with a vent hole which is arranged in order to make it possible to offset the volume of product distributed with air. As such, by allowing air to enter into the rigid reservoir, the vent hole prevents a vacuum from establishing inside said reservoir as dispensing takes place.
Plunger tubes are conventionally made from a thermoplastic material of the polyolefin type, i.e. they are not very transparent and retain the curvature of the storage reels. There are also plunger tubes made from fluoro-polymers which have the advantage of being practically invisible once immersed into a product, but remain visible when they are not immersed into a product.
In certain applications, in particular cosmetics, the visibility of the plunger tube through the wall of the bottle is deemed to be unsightly. In order to overcome this aesthetic problem, it has been proposed to use a tube cover surrounding the plunger tube over at least one portion of its length, said tube cover then able to be selected in order to have advantageous aesthetics in the reservoir, in particular through the use of a particular and/or decorative material on said tube cover, or in order to maintain the initially curved plunger tube in a precise position, for example in order to sample the last drop in a hollow made at the bottom of the bottle.
In particular, the tube cover can be associated to the body of the device for sampling by means of a bushing which has an exterior surface around which the upper end of the tube cover is arranged and an interior surface wherein said body is mounted. However, in such an assembly, the air return path between the vent hole and the reservoir passes through the product, which can cause problems with the product leaking as well as problems with the reliability of the air return function expected.
In order to attempt to resolve this problem, it has been proposed to make a hole in the tube cover. However, in addition to the cost for realising it in particular through the use of transformation in a metal tube, this hole can emerge into the product, in particular according to the length of the body and of the filling level of the reservoir.
Another solution proposes to create grooves on the exterior surface, said grooves forming an air return path between the vent hole and the lower end of the bushing which is arranged in the tube cover. However, the presence of grooves reduces the mechanical resistance of the bushing as well as the reliability of the maintaining of the tube cover on the body. Therefore, the grooves must be narrow and shallow which results in their filling at least partially with the product via the phenomenon of capillarity.
However, when there is an increase in temperature, the volume of the conditioned product increases via dilatation and even more so if it contains alcohol. This then results in a pressure inside the reservoir which, according to the rise in temperature, can commonly reach 5 or 6 bars according to the product volume/air volume ratio above the product. Furthermore, a pressure differential between the interior of the container and the exterior is also formed at altitude.
Before the use users such a bottle under pressure, the air contained in the space V1 located above the product outside of the tube cover is at the same pressure as the air contained in the space V2 located above the product in the tube cover.
When the user uses the bottle, he presses the push-button, and therefore the path towards the vent hole is open. Through the balancing of the pressures with the outside air, air contained in the volume V2 escapes through the vent hole, the pressure in V2 falls, but as the grooves are partially filled with the product, the air flow through the grooves is very low. The air pressure in V1 is applied over the surface of the product, the level of liquid rises in the space V2 and passes through the air return path to the exterior. This phenomenon takes place is a few tenths of a second and causes the product to leak.